Disc drives of the “Winchester” type are well known in the industry. Such drives use rigid discs, which are coated with a magnetizable medium for storage of digital information and a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the disc to pass under respective hydrodynamic (e.g., air) bearing disc head sliders. The sliders carry transducers, which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force, which forces the slider towards the disc surface. The gimbal is positioned between the slider and the load beam to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc. Alternatively, the gimbal can be integrated with the load beam as a single, continuous piece of material.
The slider includes a bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase which creates a hydrodynamic lifting force that counteracts the load force, and causes the slider to lift and fly above or in close proximity to the disc surface. One type of slider is a “self-loading” air bearing slider, which includes a leading taper or step, a pair of raised side rails, a cavity dam and a sub-ambient pressure cavity. The leading taper or step is typically lapped or etched onto the end of the slider that is opposite to the recording head. The leading taper pressurizes the air as the air is dragged under the slider by the disc surface. An additional effect of the leading taper is that the pressure distribution under the slider has a peak near the taper end or leading edge due to a high compression angle of the taper, and has a second peak near the recording end or trailing edge due to a low bearing clearance for efficient magnetic recording. This dual peak pressure distribution results in a bearing with a high pitch stiffness.
Some disc head sliders have included diamond-like carbon (“DLC”) pads which are formed on top of the rails to mitigate friction between the slider and the disc surface during the start and stop of disc rotation, known as contact-start-stop (CSS). Further, the DLC pads have been placed on the slider in tribologically advantageous locations to increase the relative strength of the slider. However, current DLC pads have played no role in controlling the pressurization of the air bearing surface during normal operation.
The bearing clearance between the slider and the disc surface at the recording head is an important parameter to disc drive performance. It is desired to minimize variation in head clearance or flying height. As average flying heights continue to be reduced, it is important to control several metrics of flying height performance, such as flying height sensitivity to process variations, ambient pressure (e.g., altitude) variations, changes in radial position of the slider over the disc surface and resulting head skew, and quick movements of the slider from one radial position to another radial position. In addition, it is becoming increasingly more difficult to achieve this lower fly height due to inherent limitations of slider and media process consistency. Improved slider designs are therefore desired that can account for these inherent process limitations while providing very low and stable flying heights.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.